San Diego  It has been 10 years since the costliest ecoterrorism arson in the nation ripped through the construction site of a University City housing project, a $50 million inferno that was unforgettable to anyone awakened by the towering flames.

The five-story apartment complex has long since been rebuilt, but the FBI file on the case is far from closed.

A banner left behind at the scene of the 2003 fire, as well as four others placed at another series of arsons weeks later, left no doubt it was the work of the Earth Liberation Front, an international radical environmentalist group that aimed to fight urban sprawl through economic sabotage. But identifying exactly who set the fires remains a mystery that the FBI has spent the past decade trying to solve.

These days, much of that investigation centers around the same network of activists, as agents interview and reinterview them year after year hoping something within has changed — an ideology, a relationship, a moral tug.

“If somebody truly believes and buys into that (militant) mind-set, it’s going to be difficult for us to get any kind of cooperation,” said FBI Supervisory Special Agent Keith Kelly.

“But over time, that can erode, when folks have different perspectives and different life experiences.” Kelly said. “People realize the actual environmental impact to extinguish a fire is far more damaging. Those types of things start to creep in, and it starts to help us break down those barriers.”

And then there’s the little mystery within the mystery, the color-coded clues on the backs of the banners that no one has been able to figure out.

The fires

An apartment complex at 9805 Judicial Drive was the site of an Earth Liberation Front arson 10 years ago while it was in the framing process.
— John Gastaldo

An apartment complex at 9805 Judicial Drive was the site of an Earth Liberation Front arson 10 years ago while it was in the framing process.
— John Gastaldo

The sprawling La Jolla Crossroads residential and research complex currently sits on 33 acres between the University Towne Centre mall and Interstate 805. It’s popular with University of California San Diego students and young professionals, many who have no knowledge of the complex’s explosive beginnings.

The project’s developer, Stuart Posnock, was asleep on Aug. 1, 2003, when he got a 3 a.m. call from a friend alerting him to the fire. As he drove down Mount Soledad, the predawn sky glowed ominously orange above his construction site.

He pulled up just as a 100-foot crane toppled to the ground. Flames soared 200 feet into the air, incinerating the framed 206-unit apartment complex. Hundreds of nearby residents had evacuated. Fireballs landed on neighboring patios.

No one was injured, but the fire had done its damage.

On the ground were two white bedsheets laid together, their corners weighted with heavy rocks. “If you build it — we will burn it,” the banner read. “The E.L.F.s are mad.”

The arson put other builders around the county on alert as they added security cameras and overnight guards to further protect their sites.

ELF struck again in the early morning hours of Sept. 19, 2003, at construction sites in Torrey Highlands. Four unfinished homes were destroyed and two were damaged at Shea Homes’ Avalon Point and Pardee’s Bordeaux tract. The arsonists tried to burn a third site, Western Pacific Housing’s Monaco development, but the blaze never really took off.